noun
Technical term in chemistry and distillation for a portion of a mixture separated by boiling point.
蒸留によって得られた留分を分析した。
We analyzed the fraction obtained by distillation.
この留分には目的の化合物が多く含まれている。
This fraction contains a high concentration of the target compound.
Compound of 留 (retain, stop) and 分 (part, portion), referring to the portion retained during distillation. The exact historical derivation is uncertain.